An oxygen-enriched/natural gas combustion study with a modified low NOx CGRI burner has been completed. Effects of oxygen enrichment, at various stack oxygen levels and a single furnace operating temperature, on NOx and CO2 emissions, fuel efficiency and furnace temperature distribution, were determined. Combined effects of oxygen enrichment and air infiltration were also studied. A single sidewall mounted burner was employed in the pilot scale CAGCT research furnace. The firing rate required to maintain the furnace temperature at 1100°C decreased linearly with increasing oxygen enrichment. At full oxygen enrichment, a reduction of 40-45% in the firing rate was needed to maintain constant furnace temperature. NOx emissions (< 12 mg/MJ) were relatively constant with changes in oxygen enrichment levels below ~ 60% and decreased at higher oxygen enrichment. NOx emission increased with increasing stack oxygen concentration at all oxygen enrichment levels. Air infiltration resulted in NOx emissions similar to those observed with no air infiltration but with similar stack oxygen concentrations. The standard deviation of the temperature distribution for the furnace roof and blind sidewall was in the range, 19 – 27 °C with no oxygen enrichment and 31 – 34 °C with 90% oxygen enrichment.